Ecdysteroids conjugates

The major ecdysteroid conjugate in newly-laid eggs of Locusta migratoria has been identified by spectroscopic methods as the 22-adenosine-5 -monophosphate ester of 2-deoxyecdysone (47). ... 

Figure 3. Procedure used for the Isolation of ecdysteroid conjugates from Manduca pupae.

The Isolation and Identification of free ecdysteroids from Manduca and insects in general has not been too difficult, because we had partition systems that effectively separated free ecdysteroids from their impurities. For example, from processing 130 g of pupae, the ecdysteroids which partition into the butanol phase are now present in only 413 mg of residue (Fig. 3). This material could be further purified by column and thin-layer chromatography and countercurrent distribution. On the other hand, the ecdysteroid conjugates are present in 3.74 g of residue that is water-soluble which presents additional obstacles to further purification. The nature of the conjugation or the impurities present quite often prevented successful column or thin-layer chromatography of the conjugates. More recently, however, a method was described for the separation of... 

Whiting, P., and Dinan, L. (1988). The occurrence of apolar ecdysteroid conjugates in newly-laid eggs of the house cricket, Acheta domesticus. J. Insect Physiol. 34 625-631. 

The existence of polar and nonpolar conjugates or metabolites of ecdysteroids makes it very difficult to search for them with chromatographic methods, even with linked MS. Many investigators resort to a mixture of radioimmunoassay and chromatographic methods, usually with antibodies that recognize different parts of the ecdysteroid molecule, so that conjugates with either the 3-position or the side-chain hydroxyls is blocked, can be recognized.33... 

Balance between the active and inactive forms of ecdysone and/or other ecdysteroids may be accomplished by the formation of conjugates such as sulfate esters or glucosides (20,27). The sulfation of phenols and a variety of sterols has been 3emonstrated in insect tissues and this, in close association with an appropriate sulfatase, would constitute a readily reversible mechanism whereby the required balance between active and inactive forms of ecdysteroids could be regulated (27). 

However, it is now becoming increasingly apparent that conjugation reactions may play an important physiological role in the regulation of insect ecdysteroids. Perhaps this possibility will provide the necessary stimulus for more comprehensive studies in the future. 

The concentration of ecdysteroids in the adult sheep tapeworm, Moniezia ex-pansa has been found to be 0.3-0.7 ng/g. Free and conjugated ecdysteroids have also been reported from Hymenolepis diminuta [74]. Such steroids may be found in schistosomes too [69]. 

Henk, D. F. G. Schallig, Young, N. J., Magee, R. M., deJong-Brink, M. and Rees, H. H. (1991) Identification of free and conjugated ecdysteroids in cercariae of the schistosome Trichobilharzia ocellata. Mol. Biochem. ParasitoL 49 169-176. 

Free and Conjugated Ecdysteroids in the Tobacco Hornworm, Manduca sexta, at Various Developmental Stages... 

Table II. Titer of Free and Conjugated Ecdysteroids of Ovaries and Eggs at Various Developmental Stages of the Tobacco Hornworm...

Though the ratio of 26-hydroxyecdysone to other ecdysteroids in eggs and ovaries of the THW can be as high as 20 1 (20), it was not anticipated that the C-26 hydroxyl would be the only position involved in conjugate formation. In a study In which the conjugate was labeled, RP-HPLC and radioassay analyses showed a radioactive peak preceding the peak of 26-hydroxyecdysone 26-phosphate. This... 

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